Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1999-02-03
2002-12-17
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S132000, C455S083000
Reexamination Certificate
active
06496083
ABSTRACT:
This application is a U.S. National Phase Application of PCT International Application PCT/JP98/02428.
FIELD OF THE INVENTION
The present invention relates to a dual band switch, a dual band antenna duplexer and a dual band mobile communication apparatus using the same, used mainly for a mobile communication device such as a portable telephone or the like.
BACKGROUND OF THE INVENTION
A popular convention high frequency switch is disclosed in the non-examined Japanese Patent Application Publication No. H07-321692. A conventional switch is shown in FIG.
13
. The switch of
FIG. 13
comprises a circuit connecting in parallel PIN diode
1001
and compensation circuit
1002
. Compensation circuit
1002
may be formed with a series connection of capacitor
1003
and inductor
1004
. Compensation circuit
1002
may be used for turning off the switch circuit when PIN diode
1001
is in an inactive state. Therefore, compensation circuit
1002
may be set so that inductor
1004
cancels the parasitic capacitance of PIN diode
1001
in an inactive state, and may help create parallel resonance at a desired band. Capacitor
1003
may be referred to as a DC cut element for interrupting the direct current route of the compensation circuit when PIN diode
1001
becomes active and the switch circuit is turned on. As a result, compensation circuit
1002
may be adjusted to have an impedance which is capacitive in a frequency range close to a direct current and inductive in a desired band, as well as to have one series resonance point in-between.
In recent years, the rapid increase of users of mobile communication technology has been observed. Mobile communication technology often entails obtaining a required number of telephonic communication channels. Experiments in using two band systems by one communication apparatus may therefore often be performed. For two band systems, a switch that works in two different bands may be required. A conventional high frequency switch, however, may be able to obtain a sufficient OFF state in only one band when a PIN diode is inactive. Therefore, to realize two band systems, two high frequency switches suitable for respective bands may be needed. The use of two high frequency switches may result in a large and complicated circuit, as well as a relatively expensive one.
The present invention addresses the aforementioned and other problems and aims to provide a dual band switch with which sufficient OFF states may be obtained in two different bands.
SUMMARY OF THE INVENTION
A circuit in accordance with the present invention comprises a parallel circuit including a diode and a compensation circuit. The compensation circuit is formed with a circuit having at least two series resonance points and one parallel resonance point.
A circuit in accordance with the present invention allows the impedance of the compensation circuit, which is capacitive in low frequency close to a direct current, to become inductive after the first series resonance point, whereby a parasitic capacitance of the diode is canceled in a first band. Further, the impedance of the compensation circuit becomes inductive again after the parallel resonance point and after the following series resonance point, whereby a parasitic capacitance of the diode is canceled in a second band. A dual band switch which assures sufficient OFF states in two different bands may thus be obtained with a relatively simple structure.
REFERENCES:
patent: 5748054 (1998-05-01), Tonegawa et al.
patent: 6011450 (2000-01-01), Miya
patent: S54-183246 (1978-06-01), None
patent: S60-114402 (1985-02-01), None
patent: 63-13418 (1988-01-01), None
patent: 2-108301 (1990-04-01), None
patent: 5-55803 (1993-03-01), None
patent: 5-90935 (1993-04-01), None
patent: 7-74604 (1995-03-01), None
patent: 7-321692 (1995-08-01), None
patent: 8-32303 (1996-02-01), None
patent: 09139601 (1997-05-01), None
Japanese language search report for Int'l Applin No. PCT/JP98/02428 dated Sep. 8, 1998.
Fujikawa Makoto
Kushitani Hiroshi
Takahashi Hiroshi
Yuda Naoki
Bettendorf Justin P.
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
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